This invention is in the area of methods for the treatment of hepatitis B virus (also referred to as xe2x80x9cHBVxe2x80x9d) that includes administering an effective amount of one or more of a L-2xe2x80x2 or 3xe2x80x2-azido)-2xe2x80x2,3xe2x80x2-dideoxy-5-fluorocytosine to a host in need thereof.
HBV is second only to tobacco as a cause of human cancer. The mechanism by which HBV induces cancer is unknown, although it is postulated that it may directly trigger tumor development, or indirectly trigger tumor development through chronic inflammation, cirrhosis, and cell regeneration associated with the infection.
Hepatitis B virus has reached epidemic levels worldwide. After a two to six month incubation period in which the host is unaware of the infection, HBV infection can lead to acute hepatitis and liver damage, that causes abdominal pain, jaundice, and elevated blood levels of certain enzymes. HBV can cause fulminant hepatitis, a rapidly progressive, often fatal form of the disease in which massive sections of the liver are destroyed. Patients typically recover from acute viral hepatitis. In some patients, however, high levels of viral antigen persist in the blood for an extended, or indefinite, period, causing a chronic infection. Chronic infections can lead to chronic persistent hepatitis. Patients infected with chronic persistent HBV are most common in developing countries. By mid-1991, there were approximately 225 million chronic carriers of HBV in Asia alone, and worldwide, almost 300 million carriers. Chronic persistent hepatitis can cause fatigue, cirrhosis of the liver, and hepatocellular carcinoma, a primary liver cancer. In western industrialized countries, high risk groups for HBV infection include those in contact with HBV carriers or their blood samples. The epidemiology of HBV is in fact very similar to that of acquired immunodeficiency syndrome, which accounts for why HBV infection is common among patients with AIDS or HIV-associated infections. However, HBV is more contagious than HIV.
Daily treatments with a-interferon, a genetically engineered protein, has shown promise. A human serum-derived vaccine has also been developed to immunize patients against HBV. Vaccines have been produced through genetic engineering. While the vaccine has been found effective, production of the vaccine is troublesome because the supply of human serum from chronic carriers is limited, and the purification procedure is long and expensive. Further, each batch of vaccine prepared from different serum must be tested in chimpanzees to ensure safety. In addition, the vaccine does not help the patients already infected with the virus.
A number of synthetic nucleosides have been identified which exhibit activity against HBV. The (xe2x88x92)-enantiomer of BCH-189 (2xe2x80x2,3xe2x80x2-dideoxy-3xe2x80x2-thiacytidine), known as 3TC, claimed in U.S. Pat. No. 5,539,116 to Liotta, et al., is currently in clinical trials for the treatment of hepatitis B. See also EPA 0 494 119 A1 filed by BioChem Pharma, Inc.
xcex2-2-Hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane (xe2x80x9cFTCxe2x80x9d), claimed in U.S. Pat. Nos. 5,814,639 and 5,914,331 to Liotta, et al., exhibits activity against HBV. See Furman, et al., xe2x80x9cThe Anti-Hepatitis B Virus Activities, Cytotoxicities, and Anabolic Profiles of the (xe2x88x92) and (+) Enantiomers of cis-5-Fluoro-1-[2-(Hydroxymethyl)-1,3-oxathiolane-5-yl]-Cytosinexe2x80x9d Antimicrobial Agents and Chemotherapy, December 1992, page 2686-2692; and Cheng, et al., Journal of Biological Chemistry, Volume 267(20), 13938-13942 (1992).
U.S. Pat. Nos. 5,565,438, 5,567,688 and 5,587,362 (Chu, et al.) disclose the use of 2xe2x80x2-fluoro-5-methyl-xcex2-L-arabinofuranolyluridine (L-FMAU) for the treatment of hepatitis B and Epstein Barr virus.
Penciclovir (2-amino-1,9-dihydro-9-[4-hydroxy-3-(hydroxymethyl)butyl]-6H-purin-6-one; PCV) has established activity against hepatitis B. See U.S. Pat. Nos. 5,075,445 and 5,684,153.
Adefovir (9-[2-(phosphonomethoxy)ethyl]adenine, also referred to as PMEA or [[2-(6-amino-9H-purin-9-yl)ethoxy]methylphosphonic acid), also has established activity against hepatitis B. See for example U.S. Pat. Nos. 5,641,763 and 5,142,051.
Yale University and The University of Georgia Research Foundation, Inc. disclose the use of L-FDDC (5-fluoro-3xe2x80x2-thia-2xe2x80x2,3xe2x80x2-dideoxycytidine) for the treatment of hepatitis B virus in WO 92/18517.
Other drugs explored for the treatment of HBV include adenosine arabinoside, thymosin, acyclovir, phosphonoformate, zidovudine, (+)-cyanidanol, quinacrine, and 2xe2x80x2-fluoroarabinosyl-5-iodouracil.
U.S. Pat. Nos. 5,444,063 and 5,684,010 to Emory University disclose the use of enantiomerically pure xcex2-D-1,3-dioxolane purine nucleosides to treat hepatitis B.
WO 96/40164 filed by Emory University, UAB Research Foundation, and the Centre National de la Recherche Scientifique discloses a number of xcex2-L-2xe2x80x2,3xe2x80x2-dideoxynucleosides for the treatment of hepatitis B.
WO 95/07287 also filed by Emory University, UAB Research Foundation, and the Centre National de la Recherche Scientifique discloses 2xe2x80x2 or 3xe2x80x2 deoxy and 2xe2x80x2,3xe2x80x2-dideoxy-xcex2-L-pentofuranosyl nucleosides for the treatment of HIV infection.
WO96/13512 filed by Genencor International, Inc., and Lipitek, Inc., discloses the preparation of L-ribofuranosyl nucleosides as antitumor agents and virucides.
WO95/32984 discloses lipid esters of nucleoside monophosphates as immunosuppresive drugs.
DE4224737 discloses cytosine nucleosides and their pharmaceutical uses.
Tsai, et al., in Biochem. Pharmacol. 48(7), pages 1477-81, 1994 disclose the effect of the anti-HIV agent 2xe2x80x2-xcex2-D-F-2xe2x80x2,3xe2x80x2-dideoxynucleoside analogs on the cellular content of mitochondrial DNA and lactate production.
Galvez, J. Chem. Inf. Comput. Sci. (1994), 35(5), 1198-203 describes molecular computation of xcex2-D-3xcex2-azido-2xe2x80x2,3xe2x80x2-dideoxy-5-fluorocytidine.
Mahmoudian, Pharm. Research 8(1), 43-6 (1991) discloses quantitative structure-activity relationship analyses of HIV agents such as xcex2-D-3xe2x80x2-azido-2xe2x80x2,3xe2x80x2-dideoxy-5-fluorocytidine.
U.S. Pat. No. 5,703,058 discloses (5-carboximido or 5-fluoro)-(2xe2x80x2,3xe2x80x2-unsaturated or 3xe2x80x2-modified) pyrimidine nucleosides for the treatment of HIV or HBV.
Lin, et al., discloses the synthesis and antiviral activity of various 3xe2x80x2-azido analogues of xcex2-D-nucleosides in J. Med. Chem. 31(2), 336-340 (1988).
An essential step in the mode of action of purine and pyrimidine nucleosides against viral diseases, and in particular, HBV and HIV, is their metabolic activation by cellular and viral kinases, to yield the mono-, di-, and triphosphate derivatives. The biologically active species of many nucleosides is the triphosphate form, which inhibits DNA polymerase or reverse transcriptase, or causes chain termination. The nucleoside derivatives that have been developed for the treatment of HBV and HIV to date have been presented for administration, to the host in unphosphorylated form, notwithstanding the fact that the nucleoside must be phosphorylated in the cell prior to exhibiting its antiviral effect, because the triphosphate form has typically either been dephosphorylated prior to reaching the cell or is poorly absorbed by the cell. Nucleotides in general cross cell membranes very inefficiently and are generally not very not very potent in vitro. Attempts at modifying nucleotides to increase the absorption and potency of nucleotides have been described by R. Jones and N. Bischofberger, Antiviral Research, 27 (1995) 1-17, the contents of which are incorporated herein by reference.
In light of the fact that hepatitis B virus has reached epidemic levels worldwide, and has severe and often tragic effects on the infected patient, there remains a strong need to provide new effective pharmaceutical agents to, treat humans infected with the virus that have low toxicity to the host.
Therefore, it is an object of the present invention to provide compounds, compositions and methods for the treatment of human patients or other hosts infected with HBV.
A method for the treatment of HBV infection in humans and other host animals is disclosed that includes administering an effective amount of a xcex2-L-(2xe2x80x2 or 3xe2x80x2-azido)-2xe2x80x2,3xe2x80x2-dideoxy-5-fluorocytosine nucleoside or a pharmaceutically acceptable salt, ester, or prodrug thereof, including a stabilized phosphate, administered either alone or in combination or alternation with another anti-HBV agent, optionally in a pharmaceutically acceptable carrier; In a preferred embodiment, the 2xe2x80x2 or 3xe2x80x2-azido group is in the ribosyl configuration. In a preferred embodiment, the nucleoside is provided as the indicated enantiomer and substantially in the absence of its corresponding xcex2-D-enantiomer.
In one embodiment, the active compound is xcex2-L-(2xe2x80x2-azido)-2xe2x80x2,3xe2x80x2-dideoxy-5-fluorocytosine (L-2xe2x80x2-A-5-FddC) or a pharmaceutically acceptable ester, salt or prodrug thereof of the formula: 
wherein R is H, acyl, monophosphate, diphosphate, or triphosphate, or a stabilized phosphate derivative (to form a stabilized nucleotide prodrug), and Rxe2x80x2 is hydrogen, acyl, or alkyl.
In another embodiment, the active compound is xcex2-L-(3xe2x80x2-azido)-2xe2x80x2,3xe2x80x2-dideoxy-5-fluorocytosine (L-3xe2x80x2-A-5-FddC) or a pharmaceutically acceptable ester, salt or prodrug thereof of the formula: 
wherein R is H, acyl, monophosphate, diphosphate, or triphosphate, or a stabilized phosphate derivative (to form a stabilized nucleotide prodrug), and rxe2x80x2 is hydrogen, acyl, or alkyl.
The disclosed nucleosides, or their pharmaceutically acceptable prodrugs, esters or salts or pharmaceutically acceptable formulations containing these compounds are useful in the prevention and treatment of HBV infections and other related conditions such as anti-HBV antibody positive and HBV-positive conditions, chronic liver inflammation caused by HBV, cirrhosis, acute hepatitis, fulminant hepatitis, chronic persistent hepatitis, and fatigue. These compounds or formulations can also be used prophylactically to prevent or retard the progression of clinical illness in individuals who are anti-HBV antibody or HBV-antigen positive or who have been exposed to HBV.
In one embodiment, the invention includes a method for the treatment of humans infected with HBV that includes administering an HBV treatment amount of a prodrug of the specifically disclosed L-(2xe2x80x2 or 3xe2x80x2)-A-5-FddC nucleosides. A prodrug, as used herein, refers to a pharmaceutically acceptable derivative of the specifically disclosed nucleoside, that is converted into the nucleoside on administration in vivo, or that has activity in itself. Nonlimiting examples are the 5xe2x80x2 and N4-cytosine acylated or alkylated derivatives of the active compound, as well as the 5xe2x80x2-monophosphate, diphosphate, or triphosphate derivatives, other phosphates, or stablized nucleotide prodrugs, as described in more detail below. For example, the nucleoside is provided as the monophosphate, diphosphate or triphosphate in a formulation that protects the compound from dephosphorylation. Formulations include liposomes, lipospheres, microspheres or nanospheres (of which the latter three can be targeted to infected cells).
In one embodiment of the invention, one or more of the active compounds is administered in alternation or combination with one or more other anti-HBV agents, to provide effective anti-HBV treatment. Examples of anti-HBV agents that can be used in alternation or combination therapy include but are not limited to the cis-2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane, preferably substantially in the form of the (xe2x88x92)-optical isomer (xe2x80x9cFTCxe2x80x9d, see WO 92/14743); the (xe2x88x92)-enantiomer of cis-2-hydroxymethyl-5-(cytosin-1-yl)-1,3-oxathiolane (3TC); xcex2-D-1,3-dioxolane purine nucleosides as described in U.S. Pat. Nos. 5,444,063 and 5,684,010; carbovir, interferon penciclovir and famciclovir.
Any method of alternation can be used that provides treatment to the patient. Nonlimiting examples of alternation patterns include 1-6 weeks of administration of an effective amount of one agent followed by 1-6 weeks of administration of an effective amount of a second anti-HBV agent. The alternation schedule can include periods of no treatment. Combination therapy generally includes the simultaneous administration of an effective ratio of dosages of two or more anti-HBV agents.
In light of the fact that HBV is often found in patients who are also anti-HIV antibody or HIV-antigen positive or who have been exposed to HIV, the active anti-HBV compounds disclosed herein or their derivatives or prodrugs can be administered in the appropriate circumstance in combination or alternation with anti-HIV medications.
The second antiviral agent for the treatment of HIV, in one embodiment, can be a reverse transcriptase inhibitor (a xe2x80x9cRTIxe2x80x9d), which can be either a synthetic nucleoside (a xe2x80x9cNRTIxe2x80x9d) or a non-nucleoside compound (a xe2x80x9cNNRTIxe2x80x9d). In an alternative embodiment, in the case of HIV, the second (or third) antiviral agent can be a protease inhibitor. In other embodiments, the second (or third) compound can be a pyrophosphate analog, or a fusion binding inhibitor. A list compiling resistance data collected in vitro and in vivo for a number of antiviral compounds is found in Schinazi, et al, Mutations in retroviral genes associated with drug resistance, International Antiviral News, Volume 1(4), International Medical Press 1996.
Preferred examples of antiviral agents that can be used in combination or alternation with the compounds disclosed herein for HBV therapy include 2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane (FTC); the (xe2x88x92)-enantiomer of 2-hydroxymethyl-5-(cytosin-1-yl)-1,3-oxathiolane (3TC); carbovir, acyclovir, interferon, L-FMAU, and xcex2-D-dioxolane nucleosides such as xcex2-D-dioxolanyl-guanine (DXG), xcex2-D-dioxolanyl-2,6-diaminopurine (DAPD), and xcex2-D-dioxolanyl-6-chloropurine (ACP), L-FDDC (5-fluoro-3xe2x80x2-thia-2xe2x80x2,3xe2x80x2-dideoxycytidine), L-enantiomers of 3xe2x80x2-fluoro-modified xcex2-2xe2x80x2-deoxyribonucleoside 5xe2x80x2-triphosphates, famciclovir, penciclovir, bis-Pom PMEA (adefovir, dipivoxil); lobucavir, ganciclovir, and ribavarin.
The active anti-HBV agents can also be administered in combination with antibiotics, other antiviral compounds, antifungal agents, or other pharmaceutical agents administered for the treatment of secondary infections.